CAPTURE AND HANDLING OF FREE-RANGING KOALAS

The physical capture of koalas is necessary for many eco­logical research studies, population health and reproduc­tive management and also when free-ranging koalas require active management for protection from risks associated with vegetation clearing (e.g.

3.1 Capture techniques

3.1.1 Flagging

Several techniques are used to capture free-ranging koalas. The most common, referred to as ‘flagging’ involves the use of a flag (Fig. 36.5) or fabric-covered ‘halo’ or loop (Fig. 36.6) attached to the end of a long pole, often an alu­minium swimming pool pole. Other, longer and more expensive options for flagging poles are available, includ­ing carbon fibre collapsible poles (telescoping linesman and window-cleaning poles). The flag or halo is waved above the koala, or gently tapped on its head, to encourage it to descend the tree. Flagging can be conducted from the ground if the koala is within reach or it may require climb­ing the tree or an adjacent tree. Climbing should only be conducted by trained personnel using suitable tree-climb­ing equipment.

Critical to the success of flagging is that the koala per­ceives that the threat is coming from above, rather than below. Hence, all capture personnel and observers must remain very still and quiet before and during the capture. Once the koala is aware that threats are present on the ground as well as above, the risk associated with the cap­ture attempt increases and the chances of success decrease.

Fig. 36.5. Capture using the flagging technique with a pole fitted with a soft fabric 'flag'. Alternative flag material may include plastic bags or other flexible material.

jump wildly if the capture is prolonged and/or it becomes aware of threats present on the ground. Although rare, significant injuries can occur when koalas fall or jump to the ground from considerable heights. It is important to have people on the ground with a tarpaulin or blanket

Fig. 36.6. Capture using the flagging technique with a pole fitted with an aluminium ring or 'halo' that has been fitted with a fabric cover. The halo can be used to tap or apply pressure to the koala's head when stubbornness or repeated capture predisposes the koala to ignoring the flag.

ready to catch the koala (Blanshard and Bodley 2008; NHMRC 2014). Usually, flagging captures can be con­ducted safely and rapidly when the capture team is quiet, efficient and experienced, and the capture is well planned.

Once the koala has descended to the ground, or is within easy reach, it is restrained with one hand firmly pressing down on the head and the other under the rump, forcing the koala into a ‘ball’, or by ‘scruffing’ and supporting the rump. The koala is then lifted up and off the tree or ground and placed into a koala transport box or bags. A blanket or towel can be used to facilitate removal from the tree, but most experienced koala cap­ture personnel use only their hands. Top-opening rather than side-opening transport containers are preferable. Transport containers should be well-ventilated but cov­ered with a light sheet or ‘cage cover’ to minimise visual stimulation and escape attempts. Alternatively, the koala can be gently manipulated (either after restraint or as it descends the tree if within reach) into a breathable mate­rial bag (with drawstring opening) for rapid on-site examination or short-term transport to another location (Blanshard and Bodley 2008).

Koalas that are captured and handled quietly and gently tend to become compliant and relaxed if they need managed care for disease or injury treatment, and are less likely to become excessively stressed during subsequent captures. Conversely, koalas that are handled roughly or suffer prolonged and stressful capture events, may become highly stressed patients and more problematic for future captures. The value of quiet, expert and gentle cap­ture and handling cannot be overemphasised.

3.1.2 Trapping

A modified version (Phillips 2011; Hanger et al 2017) of the koala trap designed by Hasegawa and Carrick (1995) is a very useful and safe method to use in some circum­stances. They are not suitable in uneven or steep terrain or if there is thick undergrowth. The trap is constructed using 1200-mm corrugated plastic sheeting (Corflute®, Corex, Dandenong, Vic.) supported as a temporary fence around the target tree(s) by steel or plastic rods (Fig. 36.7).

Fig. 36.7. Koala trap constructed with 1200-mm corrugated or twin-wall polypropylene plastic sheeting (e.g. Corflute®, Dandenong, Vic.) supported by steel rods, encircling the tree with a funnel leading into a treadle-activated trap.

When the koala descends the tree to move across the ground, the fencing funnels it into a treadle-activated box trap with a clear acrylic end wall. The trap has a high suc­cess rate and is particularly useful for trees, or in circum­stances where a conventional flagging capture is not suitable.

3.1.3 Guide rope

Soft rope with a loop (noose) at one end with a stop knot to prevent over-tightening has been used extensively to cap­ture free-ranging koalas, particularly in the southern states and NSW (Madani et al. 2020). Either from the ground if the koala is within reach or with someone in the tree, and with the aid of an extension pole with a hook on the end, the loop of the guide rope is placed over the head of the koala guiding it down the tree, preventing it from attempting to move into other trees or continuing to climb. Once on the ground, the koala can be grasped safely, the loop is easily removed and the koala can be placed in a sack or transport box.

Irrespective of the widespread use of this technique, significant risk of injury or death to koalas is inherent,

Fig. 36.8. Images taken using a 3G cellular camera trap set up as the trap alert device to notify researchers of the triggering of the trap. Image (a) taken as the koala descended the tree, triggering the camera, and (b) immediately after triggering of the trap. Images are sent using the 3G mobile communications network, so cameras must be in mobile service areas to work. Trap alerts using satellite communications are available for use in remote or no-service areas.

including soft tissue trauma to the Iaryngopharynx and risk of cervical injury when the koala jumps with a noose around its neck.

3.1.4 Other capture methods

Several other methods have been used to capture koalas. Projectile darts in conjunction with the use of a fireman’s life-net, blanket or tarpaulin and experienced catching team to catch immobilised koalas as they fall have been used (Lynch and Martin 2003). If the immobilised koala is within reach, it can be retrieved by hand. The use of a dart pistol or blow pipe (where darting personnel can be positioned in close proximity (<3 m) to the koala) has proven useful in situations where koalas have repeatedly failed to respond to ‘flagging’ and are positioned low in a tree (<7 m) with clear access (no lower branches) below. Darting carries the risk of injury caused by the dart, or the koala falling and colliding with branches or the ground or failing to fall after immobilisation, necessitat­ing retrieval. Generally, darting and catching should not be used as the primary capture method and should only be performed by experienced personnel. Tarpaulins or catch blankets have also been used to catch non-sedated koalas that are chased out to the periphery of a tree where they fall or jump. This method is not recommended when other suitable methods are available.

3.2 Hyperthermia during capture

Capture of free-ranging koalas should be avoided in hot weather if possible, or conducted with extreme caution. Capture attempts, regardless of ambient temperature, are often associated with a rise in body temperature as a con­sequence of the vigorous activity inherent in the capture process.

3.3 Consideration of dependent young during capture

Capture of free-ranging koalas may pose significant risk to dependent young (PY or BY) of female koalas. Although

PY are relatively well protected in the pouch, wild jumps or falls to the ground by the mother can result in severe injury to, or death of, the PY. Capture personnel should be prepared to abort a capture attempt if the potential risk to a dependent young is significant, whether a PY or BY. Also, near-independent young may be off the mother and sitting in another part of the tree or an adjacent tree. They can be missed by the capture team, resulting in separation from the mother. The mother and BY may also become separated during capture. If only one is captured and taken for processing, someone must sit under the tree and monitor the koala left behind to ensure it does not move to another tree or if it does it is followed to ensure the mother and BY are reunited. The pouch of female koalas should always be inspected and the finding of an elongated lactat­ing teat is an indication of a dependent or near-independ­ent young. In such cases, the mother should be returned to the capture tree as soon as possible.

Trap captures provide an alternative to conventional flagging capture methods in some situations in which the risk to mother and/or dependent young is considered unacceptable for a flagging capture. Double traps (con­taining a single trap fence, but two trap boxes) have been used successfully for the capture of a mother and near­independent young (Fig. 36.9).

3.2 Chemical restraint in the field

Chemical restraint of koalas is covered in Chapter 9. Alfaxalone is an ideal chemical restraint agent for field work, allowing safe immobilisation sufficient for most procedures, including physical examination, venipunc­ture and other sampling, and application of tags and telemetry devices. Induction and recovery are smooth and predictable, and supplemental doses can be given IM or IV at 0.7-1.0 mg/kg, as required. Release of koalas is safe within 1 hr of recovery to sternal recumbency. Com­binations of alfaxalone and medetomidine with atipama- zole reversal are also being used with increasing frequency (see Appendix 3). Smaller trees with rough bark may be preferable as release trees over larger trees with smooth bark. Some care should be taken with female koalas with PY, so that the dependent young is not smothered or injured during immobilisation or recovery. Emergent PY or BY can generally be left on the mother during minor procedures to avoid stress.

Inhalation agents, such as isoflurane in oxygen, and a portable anaesthetic machine may also be used for field immobilisation. This method allows for more rapid recovery, but the equipment is bulky and can be difficult to transport to some field locations.

Fig. 36.9. Double trap set-up for capture of a female and near­independent young (a). Although only one trap was required on this occasion (b), the use of a double trap is prudent when the young are nearing independence and may descend the tree separately from their mother.

3.3 Biosecurity considerations

Contamination of personnel, koala capture and handling equipment and veterinary equipment leads to a risk of transmission of pathogens between koalas and popula­tions. This risk can be managed using appropriate biose­curity procedures and cleaning/disinfection of equipment and holding facilities (WHA 2018).

4.